V型伸长翻边解析与数值研究

为了预示曲面翻边成形性能,采用有限元仿真、解析计算与人工神经网络的方法对V型零件翻边成形进行了分析.通过建立有限元模型研究了工艺参数对成形性能的影响;基于全量塑性理论及膜应变假定,推导了轴对称情况的解析计算模型;以数值模拟结果作为训练样本,建立了V型翻边成形性能预测的BP神经网络模型.研究结果表明:工艺条件对翻边成形有较大影响,其中以张角的影响最为显著;解析模型计算简便,但是只适用于零件张角较小以及相对翻边高度较小的情况;有限元仿真与人工智能相结合的BP人工神经网络模型可以快速有效地预测翻边成形性.     

A novel biomedical titanium alloy with high antibacterial property and low elastic modulus

β-type titanium alloys have attracted much attention as implant materials because of their low elastic modulus and high strength,which is closer to human bones and can avoid the problem of stress fielding and extend the lifetime of prosthetics.However,other issues,such as the infection or inflammation postimplantation,still trouble the titanium alloy's clinical application.In this paper,we developed a novel near β-titanium alloy (Ti-13Nb-13Zr-13Ag,TNZA) with low elastic modulus and strong antibacterial ability by the addition of Ag element followed by proper microstructure controlling,which could reduce the stress shielding and bacterial infections simultaneously.The microstructure,mechanical properties,corrosion resistance,antibacterial properties and cell toxicity were studied using SEM,electrochemical testing,mechanical test and cell tests.The results have demonstrated that TNZA alloy exhibited an elastic modulus of 75-87 GPa and a strong antibacterial ability (up to 98 ％ reduction) and good biocompatibility.Moreover,it was also shown that this alloy's corrosion resistance was better than that of Ti-13Nb-13Zr.All the results suggested that Ti-13Nb-13Zr-13Ag might be a competitive biomedical titanium alloy.     

The relationship between thermal decomposition properties of titanium hydride and the Al alloy melt foaming process

Using a new temperature programmed decomposition (TPD) theory and related experimental technique, a set of thermal decomposition kinetics equations of titanium hydride can be acquired by separating and simulating its TPD spectrum. According to these equations, the relation curve of decomposition quantity and time for titanium hydride at temperature of 940 K is obtained and the result coincides well with the Al alloy melt foaming process, which provides a scientific basis for controlling the Al alloy melt foam and then the Al alloy foams with different pore structure are successfully prepared.     

TA15钛合金筒-锥复合曲母线构件旋压成形工艺研究

TA15钛合金作为一种高比强度结构材料具有良好的室温和高温强度、热稳定性能,广泛应用于飞机、导弹和发动机等飞行器,实现关键受力构件的减重要求.本文针对钛合金筒-锥复合曲母线构件的特点,重点开展了TA15钛合金薄壁曲母线构件热旋压成形技术的研究,采用剪切旋压预成形,强力旋压/普通旋压多道次复合旋压终成形的工艺方案,获得了成形质量较好的TA15钛合金筒-锥复合曲母线旋压件.建立了多道次曲母线构件的有限元模型,结合旋压实验解释了强旋/普旋复合成形过程中出现的典型缺陷产生机制.对热旋压过程坯料的显微组织观察分析发现,剪切旋压对显微组织具有一定程度的晶粒破碎作用,多道次强旋/普旋复合旋压成形后显微组织沿构件轴向和切向都发生伸长.经历剪切旋压和多道次强旋普旋复合旋压成形后,坯料的微观组织更加细化,且均匀性得到改善.TA15钛合金旋压成形工件的单向拉伸实验结果表明,相对于原始坯料旋压件强度明显提高,塑性略有下降.     

Effect of aging on the tensile properties and microstructures of a near-alpha titanium alloy

The effect of aging temperature between 650 °C and 750 °C for different aging times on the tensile properties and microstructures of Ti60 alloy were studied. The results show that the strength of the alloy increases first and then decreases with the aging temperature increases from 650 °C to 750 °C. The reduction of area of the alloy is more sensitive to the aging time than elongation. With increasing aging temperature and time, the volume fracture and grain size of silicides and α₂ phase increase gradually. The silicides have the strengthen effect on the Ti60 alloy, but the effect weakens when the silicides grow up. The loss of ductility is mainly attributed to the precipitation of α₂ phase after aging treatment.     

Simulation of elevated temperature fatigue damage evolution using the finite element method for near alpha titanium alloy

The numerical estimation of evolving damage under low cycle fatigue loading condition has been performed in the near‐α titanium alloy IMI‐834 at 823 K temperature. By using the experimentally determined parameters as input, numerical simulation of fatigue damage has been performed on round specimens using finite element analysis. Coupled deformation‐damage model has been established for this alloy for simulation of damage evolution in a three‐dimensional cylindrical low cycle fatigue test specimen. The fatigue damage estimates from numerical simulation are observed to be in close agreement with the experimental results.     

有机高分子絮凝剂对钛液沉降性能的影响

针对硫酸法钛白粉生产中钛液沉降净化过程,选用不同钛液沉降用商品絮凝剂,进行钛液沉降效果实验研究.分别从有机高分子絮凝剂的分子量、阳离子度、分子结构几方面研究其对钛液沉降效果的影响.结果表明,当絮凝剂的分子量在600～800万之间,阳离子度在36%～45%之间,其对钛液的沉降效果明显;絮凝剂结构也会影响到钛液沉降效果.     

热处理对BT14钛合金显微组织和力学性能的影响

本文研究了BT14钛合金热处理规范→显微组织→力学性能之间的关系.结果表明:热处理工艺对组织和力学性能的影响很大.其中,随着退火温度的升高,初生α相含量逐渐减小,α相颗粒逐渐粗化,向等轴状发展;随着退火温度的升高,合金的强度和硬度逐渐减小,但塑性变化是先升高后减小的趋势.热处理强化规范中低温淬火 低温时效所得的合金综合性能较优.但BT14钛合金强化效果不明显.     

Measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V) by a microsecond-resolution transient technique

A microsecond-resolution pulse heating technique was used for the measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V). The method is based on rapid (50- to 100-s) resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measuring, as functions of time, current through the specimen, voltage across the specimen, and radiance of the specimen. Melting of the specimen is manifested by a plateau in the measured radiance. The time integral of the net power absorbed by the specimen during melting yields the heat of fusion. The values obtained for heat of fusion were 272 J · g^–1 (13.0 kJ · mol^–1) for titanium and 286 J · g^–1 for the alloy 90Ti-6Al-4V, with an estimated maximum uncertainty of ±6% in each value.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

Analysis of the compression process and dimensional optimization of self‐expanding stent of a nickel titanium alloy

The vascular stents are important devices introduced into the vessel to protect the lumen from unfriendly stenosis so that the blood can flow naturally. During its implantation to the vessel, the stent should be compressed to a delivery system with very small dimension to accomplish the minimal invasive operation. At this stage, the stent will withstand very large stresses which will cause large damages in the structure. In this paper, the compression process of the stent was analyzed by finite element analysis method with software ABAQUS. The stress, strain and martensite volume fraction distributions were investigated at the end compression. Results show that the stent fillets are the dangerous areas for the potential failure. Subsequently, the dimensional optimization was performed to decrease the maximum concentration stress. After the optimization, the maximum stress can be decreased by 14.2%, which means the stent's work life can be increased.